Analysis of detached cMTs by electron tomography in kar1-Δ15 cells. (A) 3D model of an α-factor–treated kar1-Δ15 cell with three single detached cMTs. Green lines indicate cMTs, purple indicates the nuclear envelope, and blue indicates the plasma membrane. Red dots indicate MT minus ends. Purple, white, and blue dots mark open MT plus ends with different conformations (flared, curled, and blunt). (A1–4) Electron tomograms of MTs and their end structures from the cell on the left. MTs were tracked using the slicer tool in the IMOD software package. (A1) Closed minus end of a single detached cMT (corresponds to the MT end labeled with A1 on the left. (A2) Open plus end of a single detached cMT (A2 on the left). (A3) Closed minus end of an nMT. (A4) Open plus end of an nMT. (A1 and A3) Red arrows denote closed MT minus ends. (A2 and A4) Purple arrows indicate open MT plus ends. (B) 3D model of another α-factor–treated kar1-Δ15 cell with two single detached cMTs. Color coding is as in A. (B1) Electron tomogram of a closed minus end of a single detached cMT (B1 on the left). (B2) Closed minus end of an nMT. (B3 and B4) Open plus ends of two nMTs. (B1–4) Color coding of arrows is as in A1–4. Bars: (A and B) 300 nm; (A1, A3, B1, and B2) 30 nm; (A2, A4, B3, and B4) 50 nm.